There are many kinds of winches for a wide variety of tasks. Among the more common kinds of winches used in industry are fixed speed reversing motor winches, hydraulic winches and eddy-current coupling winches, each of which suffer from various disadvantages.
For instance, fixed speed reversing motor winches do not allow quick and sensitive control over the cable winding operation because of the delay in the motor start-up time.
Hydraulic winches suffer from the well known operational inefficiency inherent in any hydraulically operated machinery and the requirement to continuously maintain the hoses and other componentry of the sometimes rather complex hydraulic system.
Eddy-current coupling winches are highly inefficient because of their inherent characteristic of constantly operating at 100% inefficiency. Furthermore, the eddy current coupling that drives such winches has high rotational inertia which slows the winch operating response. The eddy-current coupling componentry of such winches are also difficult to make flameproof and develop a large amount of heat during operation which may make them dangerous to use in coal mines and the like.